1. Field of the Invention
The present invention relates to a ratchet strap tightener, and more particularly to a ratchet strap tightener manufactured by a plastic injection molding process and easily assembled by manufacturers.
2. Description of Related Art
Strap tighteners are used in many applications such as packaging cargo, shipping trade, etc. to tighten straps to hold objects in place. With reference to FIG. 4, a conventional strap tightener in accordance with the prior art comprises a lever (60), body (61) and a ratchet device. The lever (60) is pivotally attached to the body (61) with the ratchet device.
The lever (60) and the body (61) have a similar structure and are made of metal. The lever (60) have two sides (not numbered) opposite to each other, two first wings (601) and a holder (602). The first wings (601) are formed at the sides of the lever (60) respectively by bending or stamping. Each first wing (601) has a through hole (not numbered), a joint edge (not numbered) and a guide (603). The through hole is defined in the first wing (601) near the joint edge of the first wing (601) and is used to pivotally connect with the body (61). The holder (602) has a hole (not shown) formed on the lever (60) between the two first wings (601). The guide (603) is defined longitudinally in the first wing (601) near the through hole.
The body (61) have two sides (not numbered) opposite to each other, two second wings (611), a holder (612) and a support bar (614). Each side of the body (61) corresponds to the respective side of the lever (60). The second wings (611) are formed at the sides of the body (61) respectively by bending or stamping. Each second wing (611) has a through hole (not numbered), a joint edge (not numbered) and a guide (613). The through hole is defined in the second wing (611) near the joint edge of the second wing (611) and is used to pivotally connect with the lever (61).
The holder (612) has a hole (not shown) and is formed on the body (61) between the two second wings (611). The guide (613) is defined longitudinally in the second wing (611) near the through hole. The support bar (614) is mounted laterally between the two second wings (611) at a distal end away from the joint edge of the second wing (611). A stationary strap loop (615) with a stationary metal ring (616) is mounted around the support bar (614).
The ratchet device includes two ratchet wheels (62), two pivot pins (63), a pawl (64), a driver (66) and two springs (65). A series of teeth (621) are formed around and a through hole (not shown) is defined in each ratchet wheel (62). The through holes in the first wings (601), the second wings (611) and the ratchet wheels (62) are aligned and a ratchet wheel (62) is mounted between the corresponding first and second wings (601, 611). The pivot pins (63) pass through the through holes, and the ratchet wheels (62) are rotatably mounted on the pivot pins (63).
The pawl (64) and the driver (66) respectively have two protrusions (641, 661) and a stub (642, 662). The pawl (64) and the driver (66) are movably and respectively mounted in the corresponding guides (603, 613) of the first and second wings (601, 611). The springs (65) are respectively mounted around the stubs (642, 662), and the stubs (642, 662) are mounted respectively in the holes in the holders (602, 612). Each protrusion (641, 661) engages one of the teeth (621) on the corresponding ratchet wheel (62). The springs (65) respectively press the pawl (64) and the driver (66) against the ratchet wheel (62) to keep the protrusions (641, 661) engaged with the teeth (621).
When the strap tightener is used to tighten a strap (71) with a running end and a fixed end, the fixed end of the strap (71) must be securely attached to the body (61). A fastening metal ring (72) connects to the stationary metal ring (616) of the stationary strap loop (615) by means of a hook (73). The running end of the strap (71) is passed around an object (not shown) and bound firmly on the pivot pin (63). When the lever (60) is pivoted toward the ratchet wheel (62), the strap (71) wound on the pivot pin (63) that rotates with the ratchet wheel (62) will be rolled onto the pivot pin (63) to tighten the strap (71).
However, the conventional ratchet strap tightener has the following shortcomings.
1. The lever (60) and the body (61) are fabricated by stamping or bending to form the wings (601, 602), the holders (602) and the guides (603), which increases the manufacturing time. The springs (65) and the stationary strap loop (615) have to be mounted on and attached to the ratchet strap tightener, which increases the assembly time.
2. When the metal strap tightener is used in polluted environment that contains salty, acidic or alkali vapors, the metal strap tightener will corrode and be damaged or wear out quickly.
3. The metal strap tightener always needs to be plated or painted to prevent rust. The plating or painting process produces contaminants that are harmful to the environment and human beings.
The present invention has arisen to mitigate or obviate the disadvantages of the conventional ratchet strap tightener.
The main objective of the present invention is to provide a light weight ratchet strap tightener that can be quickly manufactured by using a plastic injection molding process.
Another objective of the present invention is to provide a ratchet strap tightener that overcomes the rust problem of metal by making the tightener from plastic.